7.22 Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:

2BrCl (g) Br2 (g) + Cl2 (g)

for which Kc= 32 at 500 K. If initially pure BrCl is present at a concentration of
3.3 × 10
–3 mol L–1, what is its molar concentration in the mixture at equilibrium?

Let the amount of bromine and chlorine formed at equilibrium be x. The given reaction is:

2BrClgBr2g+Cl2g
Initialconc.3.3×10-300
Atequilibrium3.3×10-3-2xxx

Now, we can write,

Br2Cl2BrCl2=Kc
x×x3.3×10-3-2x2=32
x=18.678×10-3-11.32x
12.32x=18.678×10-3
x=1.5×10-3

Therefore, at equilibrium,

BrCl=3.3×10-3-2×1.5×10-3
=3.3×10-3-3.0×10-3
=0.3×10-3
=3.0×10-4molL-1